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if you take a piece of white paper into different lighting conditions it will be an objectively different color in each situation but our brains are clever enough to make us feel like it's still white it's still the same piece of paper after all to match our experience cameras have to do this too balancing the colors of an image so that a white object looks white under a given light or red object looks red and so on and the typical unit to measure the color of a light is the Kelvin which is weird because Kelvin is a unit for measuring temperature not color what temperature and the color in a photograph have to do with each other comes down to history and physics the color of photographic
lighting is given in kelvin because photographic light sources almost all used to be hot glowing things like the sun or incandescent light bulb filaments and the color of a hot glowing thing changes in direct relationship with its temperature as objects heat up they start to Glow first red hot then orange hot yellow hot white hot blue hot so hotter light is Bluer and colder light is redder it's worth noting this scientific fact often leads to confusion since we talk colloquially about warm light meaning cozy orange light and cool light meaning Bluer light even warm feeling orange light actually comes from objects with colder physical temperatures I mean still hot enough to
glow red or orange hot but not white hot or blue hot incandescent light bulb filaments are roughly around 3,000 Kelvin and the temperature of the sun's surface is roughly around 6,000 Kelvin and yes it's 6,000 Kelvin rather than 6,000 de Kelvin with Kelvin you don't say degrees anyway incandescent light bulbs and the sun aren't the only two kinds of Lights even before fluorescent lights and LEDs and lasers and so on came around there were incandescent lights of different literal temperatures and therefore different colors ranging from around 20 2700 to 3400 Kelvin candle light is closer to 2,000 Kelvin daylight can actually range from around 4500 Kelvin to above 10,000 Kelvin
depending on whether it's direct sun or shade or cloudy or partially cloudy or what time of day it is or if you're outside the Earth's atmosphere altogether the point is the light sources that a camera encounters are typically anywhere from around 2,000 to 10,000 Kelvin and the camera or film needs to account for those except it's not all about Kelvin color isn't onedimensional after all not all light sources are objects whose color comes purely from being hot think neon lights or fireworks or fireflies or fluorescent light bulbs or LEDs in addition to warm versus cold light can also be shifted towards the green side of things or the magenta side of things as you can see from a full chromaticity diagram from a
practical perspective color temperature is also reversed in a camera from the way you'd expect when you dial in the color temperature setting on a camera you're actually telling the camera to compensate for lights with that temperature if you tell your camera to color balance for a very blue 10,000 Kelvin Source it will be expecting very blue light and therefore decrease the amount of blue in the image likewise if you tell your camera to color balance for a very yellow orange 25 500 Kelvin light it'll increase the amount of blue in the image to compensate for the yellowness which leads to another potential source of confusion setting the color temperature setting of a camera too high means the camera
decreases the blue enough to get a very blue light back to white but since the lights's not that blue the correction ends up going past white resulting in an overly yellow image here's what that looks like in practice and setting the color temperature setting in the camera too low results in an overly blue image that is high color temperature camera settings often lead to Yellow images and low temperature settings lead to Blue images even though High color temperature temperat lights are blue and low color temperature lights are orange this seeming Paradox arises because the color temperature setting in a camera isn't setting the color temperature of the image it's telling the camera how to
compensate for the color temperature of the lighting and get back to white lights have colors cameras have color shifts color temperature in cameras should really be called color temperature compensation or maybe we should ditch temperature alog together and just call it what color are your lights because it's all about trying to get an object to look the color that object typically looks to human eyes independent of the color of the light falling on it's just a quir of history and physics that the color of lighting was first determined almost exclusively by the temperature of the light source and even now that it isn't we still for some reason use temperature to talk about color okay you watch to the end of this video which means there are good odds
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